Study On Fatigue Performance And Fatigue Test Method Of Engineering Structures With Durability Damage

Abstract:While withstanding fatigue loads, highways, railways, bridges and industrial plants, etc. are also suffering the harassment of durability damage such as steel corrosion, concrete carbonation, freezing and thawing and so on. Under the coupling action of durability damage and fatigue loads, fatigue damage tends to occur on these structures under the condition when the coupling effect is far beyond the structures’ultimate bearing capacity. This thesis is based on an key project of National Natural Science Foundation(Joint Found No.1361204) named "More than30tons and axle load condition of railway infrastructure dynamics characteristic and adaptability". Based on the data collection and investigation about durability damage of reinforced concrete structures in different ages, this paper has analyzed the rules of interactional influence between durability damage and fatigue performance. Meanwhile, considering steel corrosion as the main cause to durability damage, it has explored the test methods on fatigue of economical and practical corroded reinforcement. The main contents of this paper are as follows:(1) By the survey on the durability damage problems of structures built in different ages, this paper has come the changing rules of concrete carbonation, corrosion of steel bars and freeze-thawing conditions of concrete with their using ages. CoMPared with durability damage of the structures without loading fatigue, the author has also studied the rules of fatigue loading effects on durability damage, which indicates that under the action of fatigue loading, the durability damage of structure exacerbates with the growth of using life.(2) This paper has studied the mechanism about the influence of various kinds of durability damage on structure fatigue performance, proving the effect law of corrosion of steel bars, concrete carbonation, and freeze-thawing conditions of concrete on structure fatigue performance in different using ages.(3) According to an exploration about fatigue test methods of two different kinds of corrosion steels, i.e. reaction frame axial tensile fatigue test and beam frame flexure fatigue test, the results reveal that with higher success rate while less cost, reaction frame axial tensile fatigue test proves to be of higher cost performance. However, as the latest beam frame flexure fatigue test has stepped across the junction between the middle part of reinforcement and concrete, its bending stress is relatively larger, leading to a failure. Therefore, this paper has suggested adding the flexible protection pad injunction part to decrease the effect of bending stress.